Young adults carry a greater risk of developing colon and rectal cancers

The prevalence of colon and rectal cancer, which have been declining for decades in the U.S., are increasing dramatically among young and middle-aged adults, according to a new study featured in the "Journal of the National Cancer Institute."

Researchers from the American Cancer Society haven't pinpointed the exact cause of these increasing rates, but they suspect that obesity, inactivity and poor diets have something to do with it.

“Colorectal cancer had been thought a success story” because overall rates have decreased, said lead researcher Rebecca Siegel. “But it appears that under the surface, the underlying risk for colorectal cancer is rising, and it is rising pretty quickly among young adults.”

The statistics in the study are stunning. Someone born in 1990 has double the risk of being diagnosed with early colon cancer and quadruple the risk of early rectal cancer than someone born in 1950. As these young adults age, it's likely that they "will carry that risk forward," the researchers found.

Most of the nation's 135,000 annual cases and 50,000 deaths due to colon and rectal cancers still affect those over the age of 55 the most, but the prevalence among young adults has surged to 29 percent for rectal cancer and 17 percent for colon cancer.

Siegel said this means that more people are getting colon and rectal cancers in "their most productive years."

Despite the alarming findings, no health group recommends average-risk young adults to get screening tests, which are usually are conducted adults over the age of 50.